1. Field of the Invention
This invention relates to a mobile communication system, and more particularly to a digital mobile communication system which makes use of an ISDN switched network.
2. Description of the Prior Art
Conventionally, a mobile communication system is constructed with a switch for exclusive use for mobile subscribers. For instance, in order to perform a connection process of a call which is originated or terminated between a mobile subscriber which uses a mobile station and another subscriber of a fixed network, a switch for exclusive use (visitor mobile telephone switch) is first provided for each of the base stations located in a prescribed area, and these switches are connected to the fixed network (routing switched network) by way of gateway mobile telephone switches (Document 1 and Document 2).
Document 1: Kota Kinoshita, "Technique Supporting Digital Mobile Telephones - System Network Implementation Technique," Journal of the Electronic Information Communication Society of Japan, Vol. 73, No. 8, pp. 812-818, 1990.
Document 2: Minoru Tanaka, "Mobile Radiocommunication System," Japanese Patent Laid-Open No. 151136/83.
FIG. 6 is a block diagram showing an example of a conventional mobile telephone system disclosed in Document 1. Referring to FIG. 6, mobile station 11 has radio transmission and reception functions. Base stations 12a and 12b are connected to visitor mobile telephone switch 13 and perform radio communication with mobile station 11, and further per-form call connection with visitor mobile telephone switch 13. Visitor mobile telephone switch 13 has visitor control and connection functions for mobile station 11. Gateway mobile telephone switch 14 has a routing function between visitor mobile telephone switch 13 and public telephone switched network 15 including local switch 16 to which fixed subscriber 17 is connected. Home memory station 18 is connected to visitor mobile telephone switch 13 and gateway mobile telephone switch 14, and registers the specific numbers of mobile stations and location registration information.
The system of Document 2 is proposed to allow a subscriber to perform communication by way of a same terminal between different mobile radiocommunication systems such as a mobile telephone system, a portable telephone system and a cordless telephone system. Claim 1 recites a mobile telephone radio base station and a portable telephone radio base station connected to a wire communication switched network. According to an embodiment, however, base stations of the mobile telephone system and the portable telephone system are connected to switches for exclusive use for mobile telephones, and all base stations are not connected to a local switch of an ISDN switched network.